net/mlx5: fix 32-bit build

net/mlx5: fix 32-bit build

This is to fix the error:
  ```
  drivers/net/mlx5/mlx5_defs.h:14:26:
  error: format '%lx' expects argument of type 'long unsigned int',
  but argument 5 has type 'off_t {aka long long int}' [-Werror=format=]
  drivers/net/mlx5/mlx5_txq.c:569:48: note: format string is defined here
     DRV_LOG(DEBUG, "port %u: uar_mmap_offset 0x%lx"
                                                ~~^
                                                %llx
  ```
Which reproduces with gcc (Ubuntu 7.4.0-1ubuntu1~18.04.1) 7.4.0.

Fixes: 6bf10ab69be0 ("net/mlx5: support 32-bit systems")
Cc: stable@dpdk.org
Signed-off-by: Ali Alnubani <alialnu@mellanox.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>